Electron tube



March 6, 1934. R. D. DUNCAN, JR

ELECTRON TUBE Original Filed'Feb. 15, 1926 3 Sheets-Sheet 1 WQMW March 6, 1934. D, DUNCAN, JR 1,950,138

ELECTRON TUBE Original Filed Feb. 15, 1926 3 Sheets-Sheet 2 I waM March 6, 1934. R. D. DUNCAN, JR

ELECTRON TUBE Original Filed Feb. 15. 1926 3 SheetHheet 3 Patented Mar. 6, 1934 ELECTRON TUBE Robert D. Duncan, Jr., East Orange, N. J., as-

signor, by mesne assignments, to'Wired Radio, Inc., New York, N. Y., a corporation of Dela- Ware Original application February 15, 1926, Serial No. 88,279. Divided and this application September 23, 1926, Serial No. 137,351

3 Claims.

My invention relates broadly to the generation of polyphase high frequency currents, and more particularly to electron tube apparatus and circuits for the production of polyphase high frequency currents for signal transmission systems.

This is a division of my application Serial No. 88,279, filed Feb. 15, 1926, which issued on July 1, 1930 as Patent No. 1,769,018.

One of the objects of my invention is to pro- 19 vide a type of multi-element electron tube and a system of circuits by means of which direct current may be converted by the electron tube into polyphase and in particular three phase high frequency current.

Another object of my invention is to provide an electron tube structure and circuits by which m ans direct current may be converted into polyphase and in particular three phase alternating current in which all even harmonics and all triple frequency harmonics of the fundamental frequency are suppressed.

Still another object of my invention is to provide a transmission and modulation system employing a polyphase electron tube structure and system of circuits.

A further object of my invention is to provide a frequency current generation system in wh ch single phase high frequency current may be converted into polyphase high frequency cur- 39 rent for polyphase electric power transmission.

Still another object of my invention is to provide a practical construction of a polyphase high frequency current generator which may be operatcd from sources of direct current or single phase frequency current normally available for the supply of polyphase high frequency electrical energy for space radio or wired radio broadcast transmission.

still further object of my invention is to provide an electron tube structure and circuit arrangement for the production of a revolving electrostatic field from a source of single phase high frequency current which may be utilized by the interposition of related electrodes and inter- Q connecting circuits for deriving polyphase high frequency currents therefrom.

My invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 illustrates at a, an assembly and at b, c and d the separate electrodes of an electron tube generator employed in the system of my invention; Fig. 2 is a side elevation of one portion of my 55, electron tube structure; Fig. 3 illustrates a circuit arrangement for the generation of three phase high frequency energy from a source of single phase high frequency energy employing an electron tube construction in accordance with my invention; Fig. 4 illustrates diagrammatically the construction of an electron tube and circuit arrangement which I provide for the generation of three phase high frequency current with means in the circuits for balancing out the even harmonics and the triple frequency harmonics and Fig. 5 is a diagrammatic view showing the relation of current flow in the several circuits of the electron tube generator circuit of Fig. 3.

With the introduction of polyphase high frequency current transmission and reception systems the necessity for a generator of polyphase high frequency electrical energy has become essential. Applications of the polyphase generation system of my invention described herein will be more clearly understood by reference to the following patents or applications for Letters Patent: Patent No. 1,592,085 issued July 13, 1926, entitled Three phase wired radio receiving circuits; Patent No. 1,591,028, issued July 6, 1926,, entitled Duplex radio telephone system, both of said patents having been granted to Robert D. Duncan, Jr.; Patent No. 1,669,159, issued May 8, 1928, to Duncan, Isler and Barone, entitled Three phase high frequency system; the applicants copending application, Serial No. 45,131, entitled Three phase high frequency system, filed July 21, 1925 and Patent No. 1,560,505, issued November 3, 1925 to Robert D. Duncan, Jr., for Method of carrier frequency suppression.

Referring to the drawings in more detail the numeral 1 represents the filament of the electron tube system which in normal operation is heated to incandesence and which may be composed of tungsten, thoriated tungsten or any other substance which is normally employed in the manufacture of filament wire. Filament 1 runs longitudinally with the glass container 2, shown here in cylindrical form. Connections 3 illustrated in Figs. 2 and 3 are common with filament 1 and serve to convey the heating current thereto. Surrounding filament 1 at a distance therefrom and concentric therewith, is a latticed wire cylinder divided into four segments 4, 5, 6, 7, having substantially the same areas. These four segments are separated from one another by spaces 8 with their longitudinal centers displaced by In the drawings the segments are shown to be of lattice construction, that is, a grid of wires running both longitudinally and transversely. Any similar type of construction may be employed such as perforated or slotted metal plates. Segments 4, 5, 6, '7, may not be solid construction. Surrounding both filament 1 and segments 4, 5, 6, '7, and at a distance therefrom are three anode electrodes 9, 10, 11, which are made of three substantially equal segments of a hollow metallic cylinder concentric with filament 1 and segments 4, 5, 6, 7. Anode electrodes 9, 10, 11, are solid in construction, are separated from one another by spaces 12 and have their longitudinal centers displaced by angles of 120. Filament 1, grid-segments 4, 5, 6, '7, and plates 9, 10, 11, are suitably housed and supported in a hermetically sealed glass vessel indicated at 2. Vessel 2 is evacuated and the tube elements are treated so as to drive off occluded gases by any of the usual methods. Connections from filament 1 are brought out at 3-3, from grid-segments 4, 5, 6, '7, at 13, 14, 15, 16, and from plates 9, 10, 11 at 1'7, 18, 19.

The electron tube structure thus consists of. an evacuated glass vessel 2, supporting and containing a filament 1, surrounding which and concentric with which are, first, four grid-segments 4, 5, 6, '7, displaced from one another by angles of 90, and second, by three plates 9, 10, 11, displaced from one another by angles of 120. Leads for connecting with the two ends of the filament and to each of the grid-segments and to the anode electrodes are brought out through the walls of the glass and the joints suitably sealed.

By the tube construction and arrangement of anode electrodes 9, 10, 11, and the disposal of each of the electrodes within the tube, polyphase alternating current having various numbers of phases may be generated. Instead of three plate electrodes, six plate electrodes displaced from one another by angles of may be used.

The operation of the tube and associated circuits for generating three phase high frequency current is best explained in reference to Fig. 3. In this figure the tube elements are numbered as indicated in Figs. 1 and 2. In addition numeral 26 represents a battery for rendering filament l incandescent to the proper degree. One terminal of battery 26 is grounded at 2'7. The negative terminal is here indicated. 28 represents a source of single phase high frequency current, which supplies energy to circuit 30 through the means of transformer 29. Circuit 30 consists of secondary coil 32 of transformer 29, variable inductance 33, variable capacity 34, and primary coil 36 of transformer 35.. Inductively coupled to circuit 30 is a second circuit 31 consisting of secondary 37 of transformer 35, variable inductance 33 and variable capacity 39. Connected to the two terminals of capacity 34 through connections 13, 15, are the grids 4, 6, of the tube. Connected to the two terminals of capacity 39 through connections 14, 16, are the two remaining grids 5, '7, of the electron tube. Bridged across grids 4, 6, 5 and '7 are respectively high series connected resistances 4041 and 42-43, the midpoints of which are connected to the negative terminals of batteries '44 and 45, the positive terminals of which are grounded at 27. Plate 9 of the tube is connected through connection 1'7 through capacity 46 to one terminal of inductance 4'7, the other terminal of which is grounded at 2'7 through connection 48. In a similar manner, plates 10 and 11 are connected through capacities 49 and 51 to one terminal each of inductances 50 and 52 through connections 18 and 19. The remaining terminals of inductances 50 and 52 are connected with the grounded terminal of inductance 47 through the common connection 48. It will be noted that inductances 4'7, 50 and 52 are connected in the well known Y or star, three phase manner. Anode electrodes 9, 10, and 11 receive their requisite high positive voltage from source 49, here shown as a battery, the negative terminal of which is grounded at 27. The positive terminal is connected through the choke coil 200, and therethrough to the high frequency choke coils 201, 202 and 203, respectively, to plates 9, 10, 11. The anode 54 of electron tube 55 also receives its high positive voltage from battery 49 through choke 200. The filament 56 of the tube 55 is grounded at 2'7. Grid 57 is connected through the secondary 58 of speech input transformer 59, and through biasing battery 60 to the grounded terminal of filament 56. The primary 61 of transformer 59 is connected in series with microphone 62 and battery 63. It will be observed that tube55 with its associated speech input apparatus serves merely to effect modulation by voice or otherwise, of the high frequency output of tube 2 by one of the well known methods of modulation. Inductively coupled to inductances 4'7, 50, 52, are secondary inductance coils 64, 65, 66, each of which preferably has in series variable inductances 6'7, 68, 69. inductances 64, 65, 66, 6'7, 68, 69, are interconnected in A in the three phase manner. At the apexes of the A connections '70, '71, '72, are made through variable capacities '73, '74, '75, to the ultimate load for tube 2, here indicated as a three phase transmission line '76.

In Fig. 3 as well as in the other figures, circuit connections to ground 27 bring such points to the same potential and, therefore, serve as a point of common connection.

Single phase high frequency source 28, by virtue of coupling at transformers 29 and 35 will establish currents in circuits 30 and 31. With suitable adjustment of these two circuits, with the proper coupling at transformer 35, and further, with circuit 31 adjusted to be substantially in resonance with the frequency of source 28, the currents in circuits 30 and 31 may be made to differ in time phase by 90. Since the voltage developed across a capacity is given by fidt where C is the capacitance of the condenser, i the traversing current and dt the differential time, the voltages developed across capacities 34 and 39 must also be 90 out of phase. By means of connections 13-15 and 14-16 these quadra ture voltages are impressed on the grids 46 and 5'7 within the evacuated vessel 2.

Under these conditions there is then produced between and around grids 4, 5, 6, '7, which practically constitute the armatures of two condensers, in accordance with fundamental electrical theory, a rotating electric field, which revolves in synchronism with the frequency of source 28, the efiective axis of revolution being substantially the filament 1 of the tube. If the circuits 30, 31, are properly adjusted the revolving field will be circular, that is, the field will have the same value for all points, of its angular displacement, which V is a preferred condition. The electric field rotating about filament 1 will, for example, when it is directed from grid 4 to grid 6, that is, when grid 4 is positively charged and grid 6 is negatively charged, cause an increase in the flow of electrons from filament 1 to anode 9, or an increase in current from anode 9 to filament 1. 180 time degrees later the field is acting in the opposite direction resulting in a decrease in plate current from the direct current condition. The resulting current flow in circuit of anode 9 is represented diagrammatically in Fig. 5 (a). Assuming that the field revolves in a clockwise direction, 120 time degrees after it is such as to cause an increase in anode current of plate 9, it will cause a similar increase in the current to anode 10, as shown in Fig. 5 (12). Likewise 120 time degrees after this condition, it will cause a similar increase in current to anode 11 as shown in Fig. 5 (c). When the action of the field is to cause a decrease in the flow of electrons to anodes 10 and 11, a decrease in the current flowing therefrom will result. Therefore, under the action of the revolving electric field of grids 4-6, 5-7, and in accordance with the well known laws governing the flow of electrons in an evacuated space between a hot cathode and cold positively charged anodes, in the presence of varying interposed charges in the field between the hot cathode and the cold anodes, the direct current as drawn from source 49 will be converted into alternating cur rent in the branches 46-47, 49-50, 51-52, of the same frequency as the driving source, and because of the angular displacements of plates 9, 10, 11, within the tube, the three alternating components of the anode currents flowing in circuits composed of elements 46-47, 49-50 and 51-52, will differ in time phase by 120. A three phase electron tube generator of high frequency currents is thus obtained. In Fig. 3 due to the coupling between coils 47-64, 50-65 and 52-66 and to the A connection of coils 64-67, 65-68 and 66-69, three phase currents are established in the transmission lines 76.

Another way of viewing the action within the tube is that the rotating electric field produces a rotating stream or cloud of electrons to revolve about the filament 1 as an axis. When the electronic stream is made to impinge upon any one of the threeplates 9, 10, 11 a current will pass across the evacuated space to filament 1. The angular displacing by 120 of the three plates 9, 10, 11, around filament 1, by virtue of the action of the rotating electron stream provides a means for generating alternating currents in the circuits connected with plates 9, 10, 11, which will differ in time phase by 120.

The function of high resistance -41, 42-43, which may or may not be required, is to afford a leakage path to the ground filament 1 for the excess electrons which may collect on grids 4-6 and 5-7. Batteries 44 and which may or may not be required, serve to provide the proper negative biasing voltage for the grids 4-6, 5-7.

Modulation of the output of tube 2 is effected by means of tube and associated apparatus. This tube, in the well known manner, functions as an audio or speech frequency amplifier, the audiofrequency voltage developed over the choke coil 200 being applied in effect in series with the voltage of source 49 to plates 9, 10, 11. Condensers 46, 49 and 51 in accordance with usual procedure have a sufiiciently high reactance at audiofrequencies to block the flow of audiofrequency current from the paths containing them. High frequency choke coils 201, 202 and 203, together with capacities 46, 49, 51, in the usual combination form a filter for separating out the high frequency alternating and continuous components of the current to plates 9, 10, 11.

The arrangement of circuits 30, 31 of Fig. 3, for obtaining two alternating voltages differing in time phase by substantially with which to produce a revolving electric field is one which has been found to yield both flexibility and stability of operation. There are other methods of accomplishing this end, however, which are effective with the tube structure shown in Figs. 1, 2, 4. It is not the intention to limit the scope of this invention to any particular circuit or system of circuits for dephasing voltages or currents for producing the revolving electric field, as it will be understood that any method which accomplishes this may be employed in conjunction with a polyphase tube of suitable internal structure.

I have described particular methods for the production of revolving electric fields from two alternating voltages out of phase by 90. It is possible to obtain revolving electric fields under other conditions of phase displacement. The essential feature is that the phase difference in electrical degrees between the producing voltages be substantially the same as the angular dis- 1 placement between the grids which produce the revolving field. For example, with the tube structures of Figs. 1 to 4 inclusive the pairs of grids 4-6, 5-7, are displaced by 90, which is also the phase angle between the producing volt 1 ages developed over capacities 34, 39.

The tube structure shown in Fig. 4 consists of a filament 1, grids 4 -6 5 -7 similar to grids 4-6, 5-7 of Figs. 1, 2, 3, but here shown as sections of a plane instead of a cylinder, and two 1 sets each consisting of three plates, 9", 10', 11 and 9", 10", 11", also sections of planes instead of a cylinder. The grids are disposed around the filament in a 90 relationship; the plates are displaced from each other by The filament 1 1 as before, is heated to the proper degree of incandescence by means of battery 26, the negative terminal of which is grounded at 27. Grids 4 5 6 7 through leads 13 -15 and 14 -16 are assumed to be connected with condensers sim- 1 ilar to 34, 39 of Fig. 3 to obtain two voltages out of phase by 90 with which to produce a revolving electric field around grids 4 -6 5 -7 Plate 9" through lead 17" is connected through capacity 151, and inductance 152 to the ground 27 1 through common through lead 17" connection 153. .Plate 9" is likewise connected through capacity 154 and inductance 155 to ground 27 through common connection 153. In a similar manner, plates 10' and 10 through leads 18" and 18" are connected respectively, through capacities 156, 158 and inductance 157 and 159 to ground 27 through common connection 153. The same method of connection holds for plates 11", 11", through leads 19" and 19" 163, to ground 27 through common connection 153. Plates 9", 9", 10",10, 11", l receive their high positive voltage from source 164, here represented as a D. C. generator of which the negative terminal is grounded at 27, through high frequency choke coils and leads-166. It will be noted that the inductances 155, 157, 161, and 152, 159, 163, considered in order of ed, in the three phase the output inductances of the circuits ing plates 9",10', 11" and 9",10", 11". Inductively coupled with inductances 155-152, 157-159, 161-163, are respectively, inductances 1 containrespectively, through capacities 160, 162, and inductances 161, h

thereof. The balanced plate circuit 167, 168, 169, which are also connected in Y through common connection 1'10. These latter inductances operate into the final load, here rep resented as a three phase transmission line 177, through variable inductances 1'71, 1'72, 1'73, and variable capacities 174, 175, 176.

By the principles outlined herein, the revolving electric field produced by the grids 4 5 6 '7 will convert the direct current drawn from source 164 into three phase alternating current effective in the output plate circuits of the tube. The frequency of the three phase current is the same as that of the single phase source which produces the voltage utilized -for obtaining the revolving electric field of grids e 6 5 -7 Now the fundamental law of the three electrode electron tube (in this case the three electrodes comprising the filament, one grid and one plate), is well known to approximate the square relationship, that is, the plate current varies substantially as the square of the voltage applied between the grid and filament, for a given applied plate voltage. Under this condition it maybe proved and is well known that if the grid voltage is alternating, that is, a sinusoidal function, the output plate current in addition to the fundamental frequency component will contain all the even harmonics connection of Fig. l is fundamentally similar to the push-pull connection well known in the radio art, by which means the even harmonics are in opposition or balance out in their eifect upon the final output circuit. In Fig. 4 this balancing effect is obtained by virtue of the connections between the paired plates 9-9', 10-10", 11"-l1, and the usual differential placing of inductances 155-152, 157-159, 161-463, which are respectively, coupled to inductances 167, 168, 169, so that no even harmonic frequency currents will be induced in the latter. Furthermore, it is known in the electric power are that with the secondaries or output windings of three phase transformers connected Y the odd harmonics of three times the fundamental frequency and multiples of three, that is, 9, 15, El, etc., are balanced out of and do not appear in the load. Odd harmonics may be and generally present in the output circuit of an electron tube amplifier. Due to the Y connection of inductances 167, 168, 169 of Fig. 4, the triple frequency harmonics are balanced out of the load or lines 1'77.

The tube structure and circuit arrangement disclosed in Fig. 4 constitute a new means for generatirr three phase high frequency current which iree from all even harmonics and from the triple frequency harmonics and all multiples thereof. The remaining harmonics may, therefore, be of the order 5th, 7th, 11th, 13th, etc., usually of rapidly diminishing amplitudes.

The elimination or partial elimination of harmonies is very essential in multiplex transmission, either for space or wired radio, as otherwise with the displacement of fundamental frequencies to avoid inter-channel interference it is virtually impossible to simultaneously avoid beating between some of the various harmonic frequencies.

As has heretofore been pointed out, the polyphase high frequency generator of my invention has numerous applications. The apparatus may be compactly arranged in a unit which is readily installed in a power plant for super-imposing polyphase high frequency energy on polyphase transmission lines emanating from the power-plant in a wired radio broadcasting system. Likewise, the apparatus may be compactly installed in a space radio broadcasting station in systems of carrier wave suppression in which polyphase signaling energy is employed as described in one of the aforementioned copending applications for Letters Patent.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An electron tube structure comprising an evacuated container enclosing a filament, four grid electrodes and six anode electrodes, said anode electrodes constituting two sets of three each disposed around different portions of said filament, the individual anode electrodes of each set being angularly displaced around said portions of said filament by substantially 120 degrees, said grid electrodes being interposed between said filament and both or" said sets of anode electrodes and angularly displaced around said filament by substantially degrees, said filament and said electrodes being electrically insulated each from the other within said container and individual connections extending from said filament and from each of said electrodes to without said container.

2. An electron tube construction comprising an evacuated vessel, a cathode disposed therein, a plurality of independent grid electrodes extending adjacent, though insulated from said cathode, a plurality of separate sets of anode electrodes positioned adjacent, though insulated from said grid electrodes at separated points along the length thereof, said grid electrodes being greater in number than the number of anode electrodes in each of said separate sets.

3. An electron tube construction comprising an evacuated vessel, a cathode disposed therein, a set of four grid electrodes extending adjacent, though insulated from said cathode and separate sets of three anode electrodes disposed along said grid electrodes at spaced intervals, and connections extending from said electrodes outside of said evacuated vessel.

ROBERT D. DUNCAN, JR. 

